Electric discharge phenomena are in general dielectric breakdown observed in the DC circuit, and are known as a spark discharge or a corona discharge that involves emission of sounds. In these discharges, the current is converged so as to cause damages to the irradiated object, since the current density is high even when the discharged current is minor. Such discharge phenomena with the converged current are industrially utilized for automobile spark plug, etc.
Also, in the medical field, there is an electrical therapeutic apparatus utilizing a DC-type corona discharge which applies a certain level of electric current to the human body. For example, Patent Documents 1-3 disclose the technology utilizing the said DC-type corona discharge.
In addition, there is an electrical therapeutic apparatus utilizing a disruptive discharge of dielectric in the AC high voltage circuit. That is, the dielectric barrier discharge (silent discharge) is known as means for to causing planar discharge of electron in prevention of converging high electric current. In this electric discharge method, AC voltage is applied to the electrode containing dielectric material to discharge electron. For example, Patent Document 4 discloses a technology using the AC-type dielectric barrier discharge.
In industrial applications, an apparatus for producing ozone is widely used in which AC voltage is applied to dielectric electrodes arranged with a certain gap therebetween so that electron is discharged alternately from the electrodes. In addition, Patent Document 5 discloses the technology of AC-type dielectric barrier discharge.    Patent document 1 : Japanese Patent Application Laid-open No. 2001-309987    Patent document 2: Japanese Patent No. 4024227    Patent document 3: Japanese Patent Application Laid-open No. 2007-42323    Patent document 4: Japanese Patent Application Laid-open No. 11-276602    Patent document 5: Japanese Patent Application Laid-open No. 2006-324128